In the related art, an electronic device such as a digital camera or a mobile terminal with camera function is provided with a camera module including a solid-state image pickup device. The solid-state image pickup device includes a plurality of photoelectric conversion elements arranged two-dimensionally corresponding to each pixel of a picked-up image. Each of the photoelectric conversion elements photoelectrically converts incident light into a quantity of electric charges (for example, electrons) corresponding to a light-received quantity to accumulate as information indicating luminance of each pixel.
In such solid-state image pickup device, miniaturization of the photoelectric conversion element has proceeded with downsizing of the device. As the miniaturization of the photoelectric conversion element proceeds, since the number of electrons to be accumulated by each of the photoelectric conversion elements, so-called the number of saturated electrons becomes less, reproduction characteristic of the picked-up image is reduced. In solid-state image pickup device, therefore, the photoelectric conversion element capable of increasing the number of saturated electrons in a limited region is desired.